Push-pull type cables are often used to control mechanical devices on motor vehicles. For example, a vent flapper that swings between open and closed positions can be moved or adjusted by the linear movement of a push-pull control-type cable, rod or other linkage. In the case of a control cable, the cable is typically run from the vent flapper to the dashboard, where the end of the cable is accessible to the vehicle operator. A simple knob or handle is attached to the cable end so that the cable can be pulled or pushed to induce linear movement that in turn moves the vent flapper. Such an arrangement requires the handle to move a linear distance equal to the distance that the flapper is moved. Sometimes this can be a problem, due to the confined space available in a vehicle cab. Also, such an arrangement allows only a one-to-one ratio of the force required to move the cable and the force required to move the flapper. While such one-to-one ratio may be sufficient for a small vent flapper, it could be that the force requirement is too great if a vent flapper or other member of relatively large mass is to be controlled. Also, it is desirable to provide a control that can be designed to have a mechanical advantage that is either greater than, less than or equal to one, as required. Therefore, it is desirable to provide a control that can be used to translate a rotary input motion by the operator into a linear motion of a control cable, rod or other linkage, and visa versa.